Core Process Variable, Gas Process Variables, And Required Data - Emerson Micro Motion SGM Series Configuration And Use Manual

Table 2-2: Core process variable and available process variables
Available process variables
Concentration (gas purity)
Net mass flow rate
Net volume flow rate
2.3.2 Core process variable, gas process variables, and
required data
The gas process variables are calculated from a combination of measured variables,
calculated variables, process data from external devices, and user-specified values. For
each process variable that you want the meter to report, you must be able to supply all
required external data and configuration values. Specific requirements are determined by
the core process variable.
Note
The meter does not measure certain process variables directly. External devices are required for the
following process variables:
•
•
•
•
Tip
You can use temperature data from the meter or from an external device.
•
•
Table 2-3: Gas measurement when the core process variable is specific gravity
Process variable to be reported
Specific gravity
Molecular weight
Base density
Configuration and Use Manual
Default measure-
ment unit
Concentration
(% mass)
g/sec
l/sec
Line pressure
Gas composition (% CO, % CO2, % H2, % N2)
Flow rate (mass or volume)
Line temperature (only if you choose to use external temperature rather than temperature
data from the meter)
If you use temperature data from the meter, related process variables will represent the gas
inside the measurement chamber.
If you use temperature data from an external device, related process variables will represent
the gas at the location of the temperature probe.
Process data from the
meter
Specific gravity
Specific gravity
Molecular weight
Base compressibility
(continued)
Core process variable
Specific gravity Molecular weight
✓
✓
✓
Process data from ex-
ternal devices
Orientation and planning
Relative density
✓ ✓
✓ ✓
✓ ✓
User-specified values
Molecular weight of air
Base pressure
Base temperature
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